1. Field of the Invention
The present invention generally relates to illumination system using a light emitting diode array and wavelength conversion.
2. Description of the Related Art
Solid-state illumination devices such as light emitting diodes have many benefits as compared with traditional illumination sources. Light emitting diodes (LEDs) have long lifetime, high energy-efficiency, pure color characteristic, good modulation performance, and shock resistant. White-light generation using blue or UV LED to excite phosphorescent materials provides a great potential for replacing traditional light source such as incandescent lamp and even fluorescent lamp.
Although multiple LEDs can linearly scale up total output lumen, the average brightness of a simple LED array can be significantly lower as compared to a single LED due to the increase of effective emitting area. Therefore, a standard LED array has difficulties in providing sufficient brightness for many applications requiring directional beam such as projection light sources and automotive headlamps. Furthermore, as the LED chip temperature increase due to the increase of driving current, the phosphorescent material directly contacting the LED chip may reduce its wavelength converting efficiency and can even be damaged by the heat.